64 250 with possible cam issues.

[Motorelic]

Im sporting a vm26 with horribly rich jetting. 55 120. Only to achieve a crappy idle. Anything leaner and its impossible to idle. I think im trying to over come the puff of compression that enters the intake on the start of the compression stroke.

[Bevel bob]

Blowing back thro the carb,---- No valve clearance?, Sticking inlet valve? Wrong cam timing?, Too much cam duration? , ignition too advanced?. Has to be somewhere amongst that lot. After building such a fantastic bike you can't let this beat you. VM26 sounds good. Dot on top cam bevel really hard to see,easy to get wrong.

[Motorelic]

All of the marks are "lined up" they just dont all line up together. As i mentioned before at tdc the ignition marks perfectly line up with the crank. But the cam marks (though in the correct cog location) arent perfectly in line until the crank rotates about 20 degrees forward. Valve clearance is within spec. I can force the cam to be lined up by jumping one tooth on the crank bevel.

[Bevel bob]

It seems most likely that your problem is cam timing, I expect you know that it takes a number of complete revolutions of the engine to get the marks to all line up and also be at tdc on the compression stroke.. I would set up the cam timing with the piston at TDC ,20 degrees out is wrong. Treat the ignition as a totally seperate thing ,With battery/coil ignition the alternator flywheel position is no where near as relevant as the mag /alt ignition system on other models.

[Eldert]

there are more then one type bottom bevel gears . the middle one is correct for your engine

the timing dot should be in the eleven o clockposition in relation to the keyway .



Eldert

[Motorelic]

there are more then one type bottom bevel gears . the middle one is correct for your engine

the timing dot should be in the eleven o clockposition in relation to the keyway .



Eldert

Oh wow! Thats a great picture. If the one in the middle is correct, my piston will never be at tdc with the cam marks straight up and down. My key way is at 12 oclock at tdc.

[Bevel bob]

AS usual Eldert hits the jackpot!. It should be possible to set the cam timing even with the wrong part. But it give me a headache thinking about it,Hopefully Eldert will explain!.

[ducwiz]

If we work on a motor from an unknown/unreliable source (possibly assembled from mixed pieces), we must scrutinize every single part inside. Eldert's advice is likewise mandatory:

it never hurts to take readings of the camshaft timing anyway . specialy aftermarked cams you never know if the keyway is in the correct place regarding the lobes

By this, a wrong cam timing would have been identified before the motor was back in it's cradle (frame). I myself also did not know about the 3 versions of bottom gears. I rarely worked on n/c bikes, and supposedly not on a single one made up from the parts box.

@Eldert: the dots on the gears seem to mark a groove between two teeth, while the keyway always line up with a groove. It cannot be precisely measured from the photo, but if it a fact, one can easily correct his timing by engaging the gears with a one-tooth offset. Did you possibly proove this during your "Ducati career" ?

cheers Hans

[Motorelic]

My engine and its marks dont all line up at TDC. I know you have to rotate the engine 5 or so times to get the marks to line back up but the ignition marks and the cam/crank marks never line up perfectly. I cant even force them to line up. If I want the upper cam marks to be lined up at tdc i HAVE to have the lower gear off by a tooth. If i could use that gear on the left it would all be lined up.

Can anyone give me the correct way to check actual cam timing and ill report back with my readings?

Thanks so much for all of the help!

Sean

[ecurbruce]

Hi Sean, and welcome to the forum...
I don't know if this will be of any help, but I've been kinda where you are now,
If you haven't already, take a look at this thread, maybe it will be of some help, or not... viewtopic.php?f=3&t=1606&hilit=Off+one+tooth. Read through the entire post #17 in that thread.
Anyway, One tooth off on the lower bevel gear shouldn't cause the problem you're experiencing, I run my monza one tooth advanced on the lower bevel gear, and one tooth retarded on the upper bevel gear to manipulate the cam timing. One difference is this is on a mild monza cam...

Bruce